The present invention relates to a five-lens image lens system, especially to a compact lens system applied to EDR (event data recorder) of the car monitoring devices with features of wide viewing angle, smaller Fno (F number), high resolution, and short total length.
Generally, a light path formed by at least one lens or lens group, in combination with an image sensing chip such as CCD (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor) arranged on the same optical axis forms an image lens system. The image lens system may be single-lens type, double-lens type or triple-lens type. While capturing images, light from the object passes through each lens or lens group to form an image on the image sensing chip for being converted into signals that are sent to related peripheral devices. Furthermore, an IR cut-off filter is disposed in front of the image sensing chip. Or a membrane is plated on an image-side lens surface of the lens prior to the image sensing chip so as to replace the IR cut-off filter. The above image lens system is broadly applied to various monitoring systems such as car safety systems, working as the image lens of the EDR (Event Data Recorder) such as car DVR (Digital Video Recorder). However, such object lens of the monitoring systems, especially for EDR, generally has following shortcomings: limited viewing angle that has negative effects on viewing angle and range of the images being captured; larger Fno that affects brightness and resolution of the images, especially the images captured in the dark; longer total length (or height) caused by the size of the image sensing chip. Once the total length can't be minimized effectively, the volume of the lens can't be reduced and the manufacturing cost also can't be decreased. Thus effects, applications or competitiveness of the image lens system are affected. Therefore, there is a space for improvement of the image lens system applied to monitoring systems, especially EDR.